While polymers containing positive sites along their molecular chain are highly desirable materials that can be used to trap and separate anions, for example when fashioned into films, such polymers are frequently difficult to synthesize. Furthermore, the relatively few such polymers that have been prepared have tended to be unstable, being undesirably susceptible to substitution and elimination reactions. Despite such difficulties, polymers having positive sites in association therewith continue to be of interest in view of the fact that in addition to being useful as ion exchange resins, the polymers can be fabricated into membranes capable of separating negatively charged species from other materials.
Furthermore, such polymers include a demonstrated ability to conduct electricity, particularly when combined, or "doped" with substances such as tetracyanoquinodimethane, TCNQ, making it possible to employ the materials as semiconductors. Among other applications may be mentioned the coating of metals such as steel, copper, iron, aluminum and other metals standardly used throughout industry, with films of the polymers to provide the metallic substrate with protection against corrosive oxidation. In addition, the polymers can function as gas separation membranes.
As mentioned, some polymers which include positive sites along their chains have previously been known, for example, those described in the U.S. Pat. No. 3,988,158. However, the polymers there described have relatively low molecular weights. In addition, all the compounds illustrated in the patent involve aliphatic "backbone" segments, and the patent fails to teach synthesis routes capable of yielding substantially aromatic polymers. In contrast, the polymers contemplated by the instant invention have backbone chains that are substantially aromatic in character, making them far more stable.
Other polymers concerned with chains having positive sites include those described in Japanese patent 59,217,789; however, the polymers taught by the patent are not only soluble in water, but they have a relatively high ionic content, considerably limiting their usefulness in many applications such as metal coatings and membranes for chemical separation.
The polymers of this invention are synthesized under higher temperatures that afford a higher molecular weight poly-pyridinium. The polymers of this invention are also notable for their lack of solubility in water which makes them ideally suited for use as film coatings to prevent or substantially reduce metal corrosion. The use of higher temperatures to afford higher molecular weight polymers is a further distinguishing aspect of the present invention. The polymers of this invention are useful as potential solid polymer electrolytes that function in basic media which is possible because the polymer of this invention enjoy enhanced thermal and chemical stability due to the presence of the pendant aryl group. The polymer of this invention are also capable of being doped by reagents such as 7,7,8,8-tetracyanoquinodimethane resulting in a conductive polymer. Such doped polymers could find use as electrical conducting materials, as redox reagents for carrying out chemical reductions or a potential anti-degradiants to protect oxygen sensitive materials.